In order to prevent from outdoor noise pollution, outdoor dirt pollution and own personal privacy, a modern building is usually designed with enclosed space. However, the building with enclosed space will meet a difficulty to expel odor and water vapor from the indoor environment. A research shows that a relative humidity in an environment higher or lower than a range of 40-60%, which is an ideal relative humidity for human body, will form an environmental hotbed for mold, dust mites and bacteria to thus cause bad smell and even an allergic reaction of eye, skin and respiratory tract. Therefore, a common way for solving the problems of odor and the high relative humidity is to install an air conditioner having functions of both ventilation and air-drying in a bathroom where moisture and smell are most often caused.
A conventional air conditioner usually reduces humidity by mechanism which increases the moving rate of water molecules by heating the environmental air to become evaporating moisture. The heated evaporating moisture is then diffused outsides of an environmental space, such as a bathroom, through the slits of the doors, windows so as to reduce the relative humidity of indoor environment. However, the above prior process of dehumidify of the conventional air conditioner can only expel a relative small proportion of moisture through the slits since most of moisture, after evaporated by heating, will condense as water in the environmental space when the moisture contacts an object with lower temperature such as a wall. Then the condensed water will repeatedly evaporate through the same procedures again and again. As a result, the conventional air conditioner is with drawback that the dehumidifying efficiency is poor and the energy-consuming is high.